FIELD OF THE INVENTION
The invention relates to a method of identifying the stroke positions in four-stroke internal combustion engines upon startup and for synchronizing sequential fuel or ignition distribution to the cylinders, as a function of the signals of a crankshaft sensor, wherein two cylinders, with pistons each having the same position and direction of motion, always form one group of cylinders.
In order to identify the cylinders of a multicylinder internal combustion engine, signals from camshaft sensors alone, or from such sensors and additional crankshaft sensors, are typically processed in an engine control unit, as can be learned from U.S. Pat. No. 4,459,968.
Although the order of ignition of the various cylinders is fixed (such as I-III-IV-II in four-cylinder four-stroke engines), nevertheless it extends over two entire revolutions of the crankshaft (CS), with two CS reference signals per engine cycle of 720.degree. CS (also referred to as an operating cycle). Without any reference signal per engine cycle (per camshaft revolution or per two crankshaft revolutions), synchronization (unequivocal association of fuel injection and ignition with the various cylinders) is not possible, since during the same crankshaft position, for instance in a four-cylinder engine when both cylinder I and cylinder IV, or both cylinder II and cylinder III, have the same piston position and direction of piston motion, although in different engine strokes (for instance, cylinder I: compression plus ignition, and cylinder IV: expulsion of the combusted mixture, or vice versa). One engine stroke extends over 180.degree. CS.
Although the engine control unit can trigger the spark plugs and fuel injection valves in a targeted way, nevertheless initially, because of the crankshaft position alone, the correct cylinder cannot be determined exactly, since at a particular crankshaft position, either cylinder I or cylinder IV should be ignited or supplied with fuel, for instance. However, it is not known which of the two cylinders should in fact be served at that time. That would require identification of the correct cylinder (synchronization), which is typically carried out by means of a camshaft sensor.